Dishwasher

ABSTRACT

A dishwasher having a recirculation centrifugal pump impeller operated to discharge liquid at the discharge periphery of the impeller and with a discharge passage adjacent this periphery to receive liquid therefrom and having a height substantially less than the corresponding height of the spaced blades of the impeller so that liquid will flow at a greater radial velocity when leaving the impeller than in passing through the blades of the impeller.

United States Patent James G. Ruspino St. Joseph, Mich. 866,852

Oct. 16, 1969 Oct. 12, 1971 Whirlpool Corporation [72] Inventor [21 Appl. No. [22] Filed [45] Patented [73] Assignee [54] DISHWASHER 3 Claims, 2 Drawing Figs. [52] U.S.Cl 415/116, 4l5/1l9,415/191,4l7/224,134/186 [51] lnt.Cl ..F01d25/00, B08b3/00 [50] FieldofSearch 134/186,

[56] References Cited UNITED STATES PATENTS 3,134,386 5/1964 Jenkins 415/116 3,244,105 4/1966 La Flame 415/191 3,294,102 12/1966 Ruspino et al. 415/119 1,079,682 11/1913 Wintroath 415/501 1,880,101 9/1932 Meachem.. 415/209 2,581,886 1/1952 Rockwell 417/2115 3,425,355 2/1969 La Flame et a1. 134/186 3,364,860 1/1968 Schmitt et a1 134/186 FOREIGN PATENTS 989,528 5/1951 France 415/211 217,495 1/19 10 Germany 415/209 Primary Examiner-Henry F. Raduazo Attorney-Hofgren, Wegner, Allen, Stellman & McCord ABSTRACT: A dishwasher having a recirculation centrifugal pump impeller operated to discharge liquid at the discharge periphery of the impeller and with a discharge passage ad jacent this periphery to receive liquid therefrom and having a height substantially less than the corresponding height of the spaced blades of the impeller so that liquid will flow at a greater radial velocity when leaving the impeller than in passing through the blades of the impeller.

PATENTEDUCT 12 l97| DISHWASHER One of the features of this invention is to provide a dishwasher having a liquid recirculation centrifugal pump with an impeller rotatable about an axis in which the impeller has spaced blades of a height to provide an impeller clearance to blade height ratio in the range of 0.05 to 0.20 and offset the disadvantage of low radial velocity through the impeller with a discharge passage of a height less than that of the blades so that the radial velocity of the liquid is increased ,as it is discharged from the impeller.

Other features and advantages of the invention will be apparent from the following description of one embodiment thereof taken in conjunction with the accompanying drawings. Of the drawings:

FIG. 1 is a fragmentary partial vertical sectional view through the bottom of a dishwasher chamber embodying the invention.

FIG. 2 is a partial sectional view substantially along line 2 2 of FlG. l.

The dishwasher shown in the accompanying drawingsis of generally the same type as that disclosed and claimed in U.S. Pat. No. 3,294,102 assigned to the same assignee as 'the present application. In the dishwasher illustrated in the drawings there is provided a washing chamber 11 having at its bottom a liquid-collecting sump l2. Extending through a centrally located opening 13 in the bottom of the sump 12 there is a motor and pump unit 14.

This unit 14 comprises an electric motor 45 depending below the opening 13 and supported by spaced legs 15 from a discharge pump housing 16. The circular periphery of this housing 16 is resiliently supported on a rubber gasket 17 that is attached to the housing 16 and to the portion of the sump l2 surrounding the opening 13.

The discharge pump housing 16 is connected to a recirculation pump housing 18 on spaced legs 19 so as to provide an annular liquid passage 20 between the pump housing 16 and 18.

The motor 45 is provided with a drive shaft 2! extending upwardly therefrom through the discharge or drain pump housing 16 and into the recirculation housing 18. Mounted on this shaft 21 within the drain housing 16 is a drain impeller 22 of the usual type which functions on reverse rotation of the motor shaft 21 to force liquid in the customary manner from the bottom of the washing chamber 11 through a discharge conduit. This conduit 23 is provided with a ball check valve 24 which permits flow only in a direction away from the impeller 22.

Also mounted on the motor shaft 21 within the pump housing 18 is an impeller 25 for a liquid recirculation centrifugal pump with this impeller having spaced arcuately curved blades 26 of the type shown in the above U.S. Pat. No. 3,294,l02 and with the outer edges 27 of these blades describing a substantially circular periphery of the impeller 25. With this construction the impeller 25 is rotatable by the motor shaft 21 about a central vertical axis that is the same as the axis of the drive shaft 21. The blades 26 although curved as described are arranged generally radially about this axis of rotation.

While the invention is described in conjunction with a centrifugal pump having a radial flow impeller it is to be understood that the same advantages are realized in centrifugal pumps having mixed flow and radial flow impellers. Thus, the invention is applicable to centrifugal pumps with mixed flow or axial flow as well as radial flow impellers of the type described above.

The pump housing 18 is provided with a central opening 28 on the bottom that is substantially coaxial with the drive shaft 21. This opening 28 is positioned to receive liquid during recirculation rotation of the impeller 25 from the liquid passage 20 in the sump 12.

The pump housing 18 is therefore positioned in the sump l2 and is located generally beneath a filter screen 29 extending across the sump withthis screen being provided with a recessed perforated solids-collecting area 30. The pump housing 18 adjacent the circular periphery of the impeller 25 which as stated is defined by the outer blade edges.27 is provided with a radial-diflusing exit annulus 31 that surroundsthe impeller periphery and is substantially coaxial with it and with the motor drive shaft 21. This annulus 31 has a height adjacent the impeller periphery that is considerably less than the height of the blades 26 with both heights being measured in a vertical direction as viewed in FIG. 1. In preferred instances this height of the passage 31 adjacent the impeller periphery is about 30 to percent of the vertical height of the blades 26 themselves.

Located at the outer edge of the annulus 31 and communicating therewith is an exit passage 32. This exit passage overlies the impeller 25 and is defined by a generally conical cover plate 33 that extends over the impeller 25 and a substantially parallel conical pump housing top plate 34 that forms the bottom of the axial discharge conduit 35 for the washing liquid. As is explained in the above prior U.S. Pat. No. 3,294,102 this passage 35 directs the recirculation liquid through a rotatable spray arm (not shown) for spraying the liquid on the articles being cleaned during the dishwashing operation.

With the structure as described, therefore, the exit annulus 31 which receives liquid from the impeller 25 and directs it generally outwardly and radially is connected to direct the liquid into the bottom of the upwardly and inwardly sloped exit 32. Then, from the top of this exit passage the liquid is directed into the axial vertical dishwashing discharge conduit 35.

As can be seen from FIG. I, the access passage 32 is arranged at a sloped angle of less than to the plane of rotation of the impeller 25 so that the liquid exiting from the impeller and flowing outwardly through the exit annulus 3l abruptly reverses its radial flow in the annular region 36 at the outer edge of the pump housing 18 and this angle of reversal is considerably greater than 90. The abrupt reversal of radial flow of the liquid is not significantly disadvantageous as the radial velocity is low at this point due to diffusion in region 31.

The access passage 32 is provided with spaced flowstraightening curved bafiles 36 that are angled to straighten out the generally spiral flow of liquid from the rotating impeller 25 with the flow into and between the baffles being indicated by the arrows 37 and 38 of FIG. 2. These baffles preferably have sides 44 that are substantially uniformly spaced between adjacent baffles so that the liquid flow path between adjacent baffles is of substantially uniform cross sec tion, thus allowing the diffusion process to be completed in conjunction with the flow-straightening process.

With the structure as described the recirculation impeller blades 26 height is large so as to provide the desired impeller clearance to blade height ratio. This small ratio resulting from the considerable height of the blades 26 reduces the radial velocity of the liquid flowing through the impeller 25 between the blades 26. In order to counteract this the height of the exit annulus 31 adjacent the periphery 27 of the impeller is much less than the height of the blades 26 themselves so that the radial velocity of the exiting liquid is considerably increased in the annulus 31. The increase of radial velocity in this manner increases the angle of the log spiral discharge path, reduces friction losses in the flowing liquid so that the size of the pump can be reduced without sacrifice of capacity and permits increasing the impeller clearance without materially increasing loss in pump performance.

As stated above, during recirculation of the liquid by the impeller 25 the motor shaft 21 is rotated in one direction which of course rotates the drain impeller 22 in this same direction. Because the drain impeller is inefficient when operated in this direction and also because of the provision of the check valve 24 there is no reverse flow in the discharge conduit 23. Then, during drainage the direction of rotation of the motor shaft 21 is reversed so that then the drain impeller 22 draws liquid from the bottom of the sump l2 and discharges it through the conduit 23 to the drain.

In order to reduce noise in the recirculation pump during this reverse drain rotation and in order to aid the rapid emptying of the liquid-pumping system there is provided an air vent passage means in the form of a tube 39 that has a raised air entrance end 40 above the normal liquid level in the chamber 1 1 and an air exit opening 41 within the pump housing 18 adjacent the periphery 27 of the impeller 25. This air exit opening 41 is between the impeller periphery and the access passage entrance 42 which is just outwardly of the spaced baffles 43.

With the recirculation pump constructed as described the liquid flow during recirculation from the blades 26 through the exit annulus 31 is at greatly increased outwardly expanding radial velocity because of the reduced height of this annulus relative to the height of the blades 26. Then, in the region 42 at the outer edge of the annulus 31 the radial component of flow reverses to flow angularly upwardly between the bafiles 36. Because of the thickness of the battles 36 as shown in FIG. 2 the radial component of velocity of the liquid is increased by the liquid being forced through the relatively narrow passages defined by the sidewalls 44 and also by the liquid converging upwardly into the discharge conduit 35 which has a considerably smaller diameter than that of the exit annulus 31. Concurrently the tangential component of velocity of the liquid is decreasing due to the flow-straightening action of the baffles 36.

Because of the high-velocity liquid flow from the impeller as explained immediately above, the air exit opening 41 of the tube 39 can be located adjacent the impeller 27 without regard to the location of the cutwater as illustrated in the above US. Pat. No. 3,294,102 or without even requiring a cutwater which of course is absent from the pump in the illustrated embodiment.

Having described my invention as related to the embodiment shown in the accompanying drawings, it is my intention that the invention be not limited by any of the details of description, unless otherwise specified.

The embodiment of the invention in which an exclusive property or privilege is claimed is defined as follows:

1. A dishwasher, comprising: a washing chamber having a liquid-collecting sump; a liquid recirculation centrifugal pump having an impeller including blades rotatable about an axisand having a generally circular discharge periphery adjacent the discharge portion of said blades; means providing an entrance for liquid to said blades adjacent said axis; means providing an exit conduit including a diffusing exit annulus surrounding said impeller discharge periphery and substantially coaxial therewith and having a height normal to the flow through said annulus that is less than the corresponding height of said blades at said periphery and an exit passage all connected in series with each other, said impeller being rotatable in a reverse direction during drainage of liquid from said washing chamber; and air vent passage means having one end opening between said impeller discharge periphery and the exit annulus and a second end opening above the liquid level in said chamber.

2. The dishwasher of claim 1 wherein said vent passage means extends through said exit passage.

3. The dishwasher of claim 2 wherein said exit passage is provided with spaced flow-straightening bafi'les angled to straighten out the generally spiral flow of liquid from said impeller, said baffles each having a substantial thickness defined by sidewalls, and said vent passage means extends through one of said bafi'les between its said sidewalls so as not to interfere with liquid flow in said exit passage between any pair of said bafi'les. 

1. A dishwasher, comprising: a washing chamber having a liquidcollecting sump; a liquid recirculation centrifugal pump having an impeller including blades rotatable about an axis and having a generally circular discharge periphery adjacent the discharge portion of said blades; means providing an entRance for liquid to said blades adjacent said axis; means providing an exit conduit including a diffusing exit annulus surrounding said impeller discharge periphery and substantially coaxial therewith and having a height normal to the flow through said annulus that is less than the corresponding height of said blades at said periphery and an exit passage all connected in series with each other, said impeller being rotatable in a reverse direction during drainage of liquid from said washing chamber; and air vent passage means having one end opening between said impeller discharge periphery and the exit annulus and a second end opening above the liquid level in said chamber.
 2. The dishwasher of claim 1 wherein said vent passage means extends through said exit passage.
 3. The dishwasher of claim 2 wherein said exit passage is provided with spaced flow-straightening baffles angled to straighten out the generally spiral flow of liquid from said impeller, said baffles each having a substantial thickness defined by sidewalls, and said vent passage means extends through one of said baffles between its said sidewalls so as not to interfere with liquid flow in said exit passage between any pair of said baffles. 